arranged by category. Some functions appear in more
than one place.
-=over
+=over 4
=item Functions for SCALARs or strings
C<chomp>, C<chop>, C<chr>, C<crypt>, C<hex>, C<index>, C<lc>, C<lcfirst>,
-C<length>, C<oct>, C<ord>, C<pack>, C<q/STRING/>, C<qq/STRING/>, C<reverse>,
-C<rindex>, C<sprintf>, C<substr>, C<tr///>, C<uc>, C<ucfirst>, C<y///>
+C<length>, C<oct>, C<ord>, C<pack>, C<q/STRING/>, C<qq/STRING/>, C<qu/STRING/>,
+C<reverse>, C<rindex>, C<sprintf>, C<substr>, C<tr///>, C<uc>, C<ucfirst>,
+C<y///>
=item Regular expressions and pattern matching
-O File is owned by real uid.
-e File exists.
- -z File has zero size.
- -s File has nonzero size (returns size).
+ -z File has zero size (is empty).
+ -s File has nonzero size (returns size in bytes).
-f File is a plain file.
-d File is a directory.
Example:
while (<>) {
- chop;
+ chomp;
next unless -f $_; # ignore specials
#...
}
# ...
}
+If VARIABLE is a hash, it chomps the hash's values, but not its keys.
+
You can actually chomp anything that's an lvalue, including an assignment:
chomp($cwd = `pwd`);
=item chop
Chops off the last character of a string and returns the character
-chopped. It's used primarily to remove the newline from the end of an
-input record, but is much more efficient than C<s/\n//> because it neither
+chopped. It is much more efficient than C<s/.$//s> because it neither
scans nor copies the string. If VARIABLE is omitted, chops C<$_>.
-Example:
-
- while (<>) {
- chop; # avoid \n on last field
- @array = split(/:/);
- #...
- }
-
-You can actually chop anything that's an lvalue, including an assignment:
+If VARIABLE is a hash, it chops the hash's values, but not its keys.
- chop($cwd = `pwd`);
- chop($answer = <STDIN>);
+You can actually chop anything that's an lvalue, including an assignment.
If you chop a list, each element is chopped. Only the value of the
last C<chop> is returned.
You may also use C<defined(&func)> to check whether subroutine C<&func>
has ever been defined. The return value is unaffected by any forward
-declarations of C<&foo>.
+declarations of C<&foo>. Note that a subroutine which is not defined
+may still be callable: its package may have an C<AUTOLOAD> method that
+makes it spring into existence the first time that it is called -- see
+L<perlsub>.
Use of C<defined> on aggregates (hashes and arrays) is deprecated. It
used to report whether memory for that aggregate has ever been
When called in list context, returns a 2-element list consisting of the
key and value for the next element of a hash, so that you can iterate over
-it. When called in scalar context, returns the key for only the "next"
+it. When called in scalar context, returns only the key for the next
element in the hash.
Entries are returned in an apparently random order. The actual random
C<keys>, and C<values> function calls in the program; it can be reset by
reading all the elements from the hash, or by evaluating C<keys HASH> or
C<values HASH>. If you add or delete elements of a hash while you're
-iterating over it, you may get entries skipped or duplicated, so don't.
+iterating over it, you may get entries skipped or duplicated, so
+don't. Exception: It is always safe to delete the item most recently
+returned by C<each()>, which means that the following code will work:
+
+ while (($key, $value) = each %hash) {
+ print $key, "\n";
+ delete $hash{$key}; # This is safe
+ }
The following prints out your environment like the printenv(1) program,
only in a different order:
Given an expression that specifies the name of a subroutine,
returns true if the specified subroutine has ever been declared, even
if it is undefined. Mentioning a subroutine name for exists or defined
-does not count as declaring it.
+does not count as declaring it. Note that a subroutine which does not
+exist may still be callable: its package may have an C<AUTOLOAD>
+method that makes it spring into existence the first time that it is
+called -- see L<perlsub>.
print "Exists\n" if exists &subroutine;
print "Defined\n" if defined &subroutine;
=item local EXPR
You really probably want to be using C<my> instead, because C<local> isn't
-what most people think of as "local". See L<perlsub/"Private Variables
-via my()"> for details.
+what most people think of as "local". See
+L<perlsub/"Private Variables via my()"> for details.
A local modifies the listed variables to be local to the enclosing
block, file, or eval. If more than one value is listed, the list must
most cases. See also L</grep> for an array composed of those items of
the original list for which the BLOCK or EXPR evaluates to true.
+C<{> starts both hash references and blocks, so C<map { ...> could be either
+the start of map BLOCK LIST or map EXPR, LIST. Because perl doesn't look
+ahead for the closing C<}> it has to take a guess at which its dealing with
+based what it finds just after the C<{>. Usually it gets it right, but if it
+doesn't it won't realize something is wrong until it gets to the C<}> and
+encounters the missing (or unexpected) comma. The syntax error will be
+reported close to the C<}> but you'll need to change something near the C<{>
+such as using a unary C<+> to give perl some help:
+
+ %hash = map { "\L$_", 1 } @array # perl guesses EXPR. wrong
+ %hash = map { +"\L$_", 1 } @array # perl guesses BLOCK. right
+ %hash = map { ("\L$_", 1) } @array # this also works
+ %hash = map { lc($_), 1 } @array # as does this.
+ %hash = map +( lc($_), 1 ), @array # this is EXPR and works!
+
+ %hash = map ( lc($_), 1 ), @array # evaluates to (1, @array)
+
+or to force an anon hash constructor use C<+{>
+
+ @hashes = map +{ lc($_), 1 }, @array # EXPR, so needs , at end
+
+and you get list of anonymous hashes each with only 1 entry.
+
=item mkdir FILENAME,MASK
=item mkdir FILENAME
kept private (mail files, for instance). The perlfunc(1) entry on
C<umask> discusses the choice of MASK in more detail.
+Note that according to the POSIX 1003.1-1996 the FILENAME may have any
+number of trailing slashes. Some operating and filesystems do not get
+this right, so Perl automatically removes all trailing slashes to keep
+everyone happy.
+
=item msgctl ID,CMD,ARG
Calls the System V IPC function msgctl(2). You'll probably have to say
sysopen(HANDLE, $path, O_RDWR|O_CREAT|O_EXCL)
or die "sysopen $path: $!";
$oldfh = select(HANDLE); $| = 1; select($oldfh);
- print HANDLE "stuff $$\n");
+ print HANDLE "stuff $$\n";
seek(HANDLE, 0, 0);
print "File contains: ", <HANDLE>;
=item qr/STRING/
-=item qx/STRING/
+=item qu/STRING/
=item qw/STRING/
+=item qx/STRING/
+
Generalized quotes. See L<perlop/"Regexp Quote-Like Operators">.
=item quotemeta EXPR
=item read FILEHANDLE,SCALAR,LENGTH
Attempts to read LENGTH bytes of data into variable SCALAR from the
-specified FILEHANDLE. Returns the number of bytes actually read,
-C<0> at end of file, or undef if there was an error. SCALAR will be grown
-or shrunk to the length actually read. An OFFSET may be specified to
-place the read data at some other place than the beginning of the
-string. This call is actually implemented in terms of stdio's fread(3)
-call. To get a true read(2) system call, see C<sysread>.
+specified FILEHANDLE. Returns the number of bytes actually read, C<0>
+at end of file, or undef if there was an error. SCALAR will be grown
+or shrunk to the length actually read. If SCALAR needs growing, the
+new bytes will be zero bytes. An OFFSET may be specified to place
+the read data into some other place in SCALAR than the beginning.
+The call is actually implemented in terms of stdio's fread(3) call.
+To get a true read(2) system call, see C<sysread>.
=item readdir DIRHANDLE
it, or else see L</select> above. The Time::HiRes module from CPAN
may also help.
-See also the POSIX module's C<sigpause> function.
+See also the POSIX module's C<pause> function.
=item socket SOCKET,DOMAIN,TYPE,PROTOCOL
If you're using strict, you I<must not> declare $a
and $b as lexicals. They are package globals. That means
if you're in the C<main> package and type
-
+
@articles = sort {$b <=> $a} @files;
-
+
then C<$a> and C<$b> are C<$main::a> and C<$main::b> (or C<$::a> and C<$::b>),
but if you're in the C<FooPack> package, it's the same as typing
produces the output 'h:i:t:h:e:r:e'.
+Empty leading (or trailing) fields are produced when there positive width
+matches at the beginning (or end) of the string; a zero-width match at the
+beginning (or end) of the string does not produce an empty field. For
+example:
+
+ print join(':', split(/(?=\w)/, 'hi there!'));
+
+produces the output 'h:i :t:h:e:r:e!'.
+
The LIMIT parameter can be used to split a line partially
($login, $passwd, $remainder) = split(/:/, $_, 3);
open(PASSWD, '/etc/passwd');
while (<PASSWD>) {
- ($login, $passwd, $uid, $gid,
+ chomp;
+ ($login, $passwd, $uid, $gid,
$gcos, $home, $shell) = split(/:/);
#...
}
-(Note that $shell above will still have a newline on it. See L</chop>,
-L</chomp>, and L</join>.)
=item sprintf FORMAT, LIST
h interpret integer as C type "short" or "unsigned short"
If no flags, interpret integer as C type "int" or "unsigned"
+Perl supports parameter ordering, in other words, fetching the
+parameters in some explicitly specified "random" ordering as opposed
+to the default implicit sequential ordering. The syntax is, instead
+of the C<%> and C<*>, to use C<%>I<digits>C<$> and C<*>I<digits>C<$>,
+where the I<digits> is the wanted index, from one upwards. For example:
+
+ printf "%2\$d %1\$d\n", 12, 34; # will print "34 12\n"
+ printf "%*2\$d\n", 12, 3; # will print " 12\n"
+
+Note that using the reordering syntax does not interfere with the usual
+implicit sequential fetching of the parameters:
+
+ printf "%2\$d %d\n", 12, 34; # will print "34 12\n"
+ printf "%2\$d %d %d\n", 12, 34; # will print "34 12 34\n"
+ printf "%3\$d %d %d\n", 12, 34, 56; # will print "56 12 34\n"
+ printf "%2\$*3\$d %d\n", 12, 34, 3; # will print " 34 12\n"
+ printf "%*3\$2\$d %d\n", 12, 34, 3; # will print " 34 12\n"
+
There are also two Perl-specific flags:
- V interpret integer as Perl's standard integer type
- v interpret string as a vector of integers, output as
- numbers separated either by dots, or by an arbitrary
- string received from the argument list when the flag
- is preceded by C<*>
+ V interpret integer as Perl's standard integer type
+ v interpret string as a vector of integers, output as
+ numbers separated either by dots, or by an arbitrary
+ string received from the argument list when the flag
+ is preceded by C<*>
Where a number would appear in the flags, an asterisk (C<*>) may be
used instead, in which case Perl uses the next item in the parameter
=item tell
-Returns the current position for FILEHANDLE. FILEHANDLE may be an
-expression whose value gives the name of the actual filehandle. If
-FILEHANDLE is omitted, assumes the file last read.
+Returns the current position for FILEHANDLE, or -1 on error. FILEHANDLE
+may be an expression whose value gives the name of the actual filehandle.
+If FILEHANDLE is omitted, assumes the file last read.
+
+The return value of tell() for the standard streams like the STDIN
+depends on the operating system: it may return -1 or something else.
+tell() on pipes, fifos, and sockets usually returns -1.
There is no C<systell> function. Use C<sysseek(FH, 0, 1)> for that.
FIRSTKEY this
NEXTKEY this, lastkey
DESTROY this
+ UNTIE this
A class implementing an ordinary array should have the following methods:
SPLICE this, offset, length, LIST
EXTEND this, count
DESTROY this
+ UNTIE this
A class implementing a file handle should have the following methods:
WRITE this, scalar, length, offset
PRINT this, LIST
PRINTF this, format, LIST
+ BINMODE this
+ EOF this
+ FILENO this
+ SEEK this, position, whence
+ TELL this
+ OPEN this, mode, LIST
CLOSE this
DESTROY this
+ UNTIE this
A class implementing a scalar should have the following methods:
FETCH this,
STORE this, value
DESTROY this
+ UNTIE this
Not all methods indicated above need be implemented. See L<perltie>,
L<Tie::Hash>, L<Tie::Array>, L<Tie::Scalar>, and L<Tie::Handle>.
If no C<unimport> method can be found the call fails with a fatal error.
-See L<perlmod> for a list of standard modules and pragmas. See L<perlrun>
+See L<perlmodlib> for a list of standard modules and pragmas. See L<perlrun>
for the C<-M> and C<-m> command-line options to perl that give C<use>
functionality from the command-line.
If BITS is 16 or more, bytes of the input string are grouped into chunks
of size BITS/8, and each group is converted to a number as with
-pack()/unpack() with big-endian formats C<n>/C<N> (and analoguously
+pack()/unpack() with big-endian formats C<n>/C<N> (and analogously
for BITS==64). See L<"pack"> for details.
If bits is 4 or less, the string is broken into bytes, then the bits
extend the string with sufficiently many zero bytes. It is an error
to try to write off the beginning of the string (i.e. negative OFFSET).
+The string should not contain any character with the value > 255 (which
+can only happen if you're using UTF8 encoding). If it does, it will be
+treated as something which is not UTF8 encoded. When the C<vec> was
+assigned to, other parts of your program will also no longer consider the
+string to be UTF8 encoded. In other words, if you do have such characters
+in your string, vec() will operate on the actual byte string, and not the
+conceptual character string.
+
Strings created with C<vec> can also be manipulated with the logical
operators C<|>, C<&>, C<^>, and C<~>. These operators will assume a bit
vector operation is desired when both operands are strings.
projects / p5sagit/p5-mst-13.2.git / blobdiff